class Dog():
    """一次模拟小狗的简单尝试"""
    def __init__(self,name,age):
        """初始化属性name和age"""
        self.name = name
        self.age = age
    def sit(self):
        """模拟小狗被命令蹲下"""
        print(self.name.title()+"is now sitting.")

    def roll_over(self):
        """模拟小狗被命令时打滚"""
        print(self.name.title()+"rolled over!")

        my_dog = Dog('willie',6)
        print("My dog's name is" + my_dog.name.title()+".")
        print("My dog is " + str(my_dog.age)+"years.old.")
        my_dog.sit()
        my_dog.roll_over()